Experimental verification of beam deflection from hybrid reflector antenna within wide-angle sector

An experiment with a hybrid reflector antenna was performed for the purpose of correlating actual beam deflections through a wide range of angles with theoretical calculations on the basis of the geometrical optics approximation. A special antenna was built for this experiment, allowing up to 30 deg deflections of a 1 deg wide beam. It consisted of a radiator in the form of an accurate E-plane waveguide array and an asymmetric reflector in the shape of a parabolic cylinder. Excitation amplitudes and phases were regulated by means of dielectric and dissipative matching inserts in the waveguides. The near-field region was probed by the compensation method in an anechoic chamber, diffraction components and edge waves as well as interference of the latter with the geometrical optics field causing oscillations of the readings and attendant deviations from theory. The error of the geometrical optics approximation is found not to exceed the error of measurements and not to depend on the deflection angle. At small deflection angles the geometrical optics approximation characterizes a spherical wave, indicating the size and the position of the radiator as the deflection angle approaches zero. At large deflection angles the approximation yields more asymmetric side lobes.